Vehicle information communication systems (VICS) and probe car information systems are known in which information about vehicle speeds, time and the like is gathered and traffic information is generated. In a probe car information system, information about speeds at which a vehicle has actually run on a road and its position is collected to generate traffic information indicating congestions or the like (see Japanese Laid-Open Patent Application No. 2003-281674, for example; hereafter referred to as Patent Document 1).
In the probe car information system discussed in Patent Document 1, an average speed and chronological changes in the position of a vehicle is calculated based on vehicle information relating to the position of the vehicle and the corresponding time, thereby generating congestion information. Further, the vehicle information is divided at predetermined time intervals into transport groups that are partially overlapped. When the average speed in a particular transport group is within a predetermined speed range, the length of the transport group is calculated in terms of a congestion length or average speed.
The above publication states that in this way, factors unrelated to a congestion, such as turns or lane changes made by a vehicle running ahead of a vehicle of interest, temporary vehicle stops necessitated by jaywalking pedestrians, or a temporary acceleration following such temporary stops, can be removed, so that an accurate congestion length can be determined.
However, in the probe car information system of Patent Document 1, the traffic signal waiting time is not subtracted from the transit time between predetermined points, such as intersections. As a result, the average speed is influenced by the stops required by the traffic signals, thus making it difficult to generate highly accurate congestion information.
It is a general object of the present invention to provide a traffic information generating method, a traffic information generating apparatus, a display, a navigation system, and an electronic control unit, whereby accurate traffic information can be generated by removing the influence or speed drops due to factors other than a congestion, such as the stops made at the traffic signals.